This application is based on Japanese Patent Application No. 2009-084029 filed on Mar. 31, 2009 and No. 2009-081499 filed on Mar. 30, 2009, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an image forming apparatus such as a digital copy machine, laser printer and the like, and more particularly, to an image forming apparatus that has a mechanism for opening and closing a paper sheet supply tray that is used to carry a sheet to an image forming portion.
2. Description of the Related Art
In some conventional image forming apparatuses, a paper-sheet carry path is formed in a vertical direction by using a carry guide to carry a paper sheet in the vertical direction. Besides, for a resolution process of jam in such a paper-sheet carry path and the like, the carry guide is supported by a shaft to be freely opened and closed, and a side cover that is freely opened and closed is disposed at a position that faces the carry guide which forms the paper-sheet carry path. Besides, in some cases, a manual supply tray (paper-sheet supply tray) is disposed on part of the side cover, and the uppermost surface of paper sheets placed on the manual supply tray is pressurized against a paper-sheet supply roller by a lift plate to perform paper-sheet supply.
In such image forming apparatuses, the carry guide, the side cover and the manual supply tray are not supported by the same support shaft. For example, JP-A-2002-214860 ([1.]) discloses a technology in which that a main component body of a both-side carry unit is formed of a resin and doubles as an exterior cover (side cover), so that the weight of the both-side carry unit and the number of parts are dramatically reduced to simplify the structures of a unit support member and the like, and positional accuracy of a carry roller is raised to allow stable paper-sheet supply. In this patent document [1.] the manual paper-sheet supply unit (paper-sheet supply tray) is supported by a shaft at a position higher than the both-side carry unit (side cover).
Besides, JP-A-2005-343700 ([2.]) discloses a technology in which a paper-sheet carry means that carries a paper sheet upward, an opening panel (side cover) that is disposed on a side of a casing to be freely opened and closed, and a manual supply tray that is disposed to be freely opened at a lower position of the opening panel and able to supply a placed paper sheet to the paper-sheet carry means in a time of being opened are disposed, so that size reduction is achieved and installation space is made small. Besides, in this patent document [2.], the paper-sheet carry means is unitarily formed with the opening panel to be freely opened and closed about a lower end that is used as a pivot; however, the manual supply tray is supported by a shaft at a position lower than the opening panel.
Besides, JP-A-2005-055862 ([3.]) discloses a technology in which first and second cover portions that are rotatable from a closing position to an opening position form first and second carry paths in parallel; a side of the first cover forms part (side cover) of a housing; first and second engagement means engage the first and second cover portions with the apparatus main body; the first engagement means is operated to together with the second engagement means in response to rotation between the closing position and the opening position, so that when a cover member that defines the first and second carry paths is opened or closed, it is possible to smoothly open or close the cover member. In this patent document [3.], a state in which the manual supply tray is supported by a shaft is not disclosed.
On the other hand, in such an image forming apparatus, rotary members such as the carry guide, the side cover, the manual supply tray and the like are rotatably supported in the apparatus main body by using a support shaft as shown in FIG. 17, for example. Specifically, a rear-side end portion 51a of a first shaft 51 that is formed into a D shape in section is inserted into a first through-hole 61a that is disposed through a rear-side wall 61 and formed into substantially the same shape in section as the rear-side end portion 51a; a come-off-preventive stop ring 55 is mounted from outside (left side in the figure) in a shaft direction, so that the rear-side end portion 51a is fixed.
Here, a front-side end portion 51b protrudes beyond a second through-hole 62a that is formed through a front-side wall 62; a first bearing 70 that is inserted onto the front-side end portion 51b is inserted into the second through-hole 62a; and the stop ring 55 is mounted from outside (right side in the figure) in the shaft direction like in the above description, so that the front-side end portion 51b is fixed.
Here, in such a technology, by reducing a clearance between an inner diameter of the first through-hole 61a and an outer diameter of the rear-side end portion 51a, positional accuracy of the first shaft 51 is raised. Accordingly, an inner diameter of the second through-hole 62a through which the first shaft 51 penetrates at the front-side side wall 62 is enlarged, so that it is made easy to insert the first shaft 51 from the front-side wall 62 to the rear-side wall 61 in a time of assembly and easy to insert the rear-side end portion 51a into the first through-hole 61a. And, the first bearing 70 through which the front-side end portion 51b penetrates is inserted into the second through-hole 62a, so that the first shaft 51 is supported.
However, because the above stop ring is used, the number of parts increases and mounting tools become necessary. Besides, because both end portions of the support shaft are situated in small places, that is, the front-side and rear-side end portions of the apparatus main body, it is hard to mount the stop ring and the like. To avoid this, a technology for fixing the bearing without using the stop ring is proposed.
For example, JP-A-1996-169588 ([4.]) discloses a technology in which two come-off-preventive protrusion portions for bearings are inserted into oblong bearing support openings (holes) formed through support walls until a state in which the come-off-preventive protrusion portions engage with side walls of the oblong bearing support openings to be prevented from coming off; a snap fit portion and an engagement portion formed on the support wall are snap-fitted to each other to prevent the bearing from rotating in a shaft rotation direction, so that with a simple structure and without using special tools and parts, the mounting and demounting of the shaft are made possible and the operability is improved at low cost.